Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2000-06-27
2002-04-09
Koczo, Michael (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
Reexamination Certificate
active
06368070
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable displacement compressor, and more specifically, to a variable displacement compressor with an improved structure for suppressing axial vibration of a drive shaft.
2. Description of Related Art
Variable displacement compressors, particularly, variable displacement inclined plate compressors, are known in the art. For example, a known structure of a variable displacement inclined plate compressor is constructed as depicted in FIG.
2
. In
FIG. 2
, variable displacement inclined plate compressor
1
′ has cylindrical housing
2
, front end plate
3
closing the front end of housing
2
, and cylinder head
4
closing the rear end of housing
2
. Valve plate
5
is interposed between the rear end of housing
2
and cylinder head
4
. Cylinder block
6
is disposed in the rear half of housing
2
. A plurality of cylinder bores
7
, center bore
8
, and communication path
9
, are formed in cylinder block
6
. Cylinder bores
7
are arranged radially about a center axis of the compressor at even radial intervals. Cylinder bores
7
extend in a front/rear direction. The front half of housing
2
forms crank chamber
10
.
Drive shaft
11
extends into housing
2
in the front/rear direction through front end plate
3
. The rear end portion of drive shaft
11
is inserted into center bore
8
. Drive shaft
11
is rotatably supported by front end plate
3
via radial bearing
12
and by cylinder block
6
via radial bearing
13
. The rear end of drive shaft
11
is axially supported by thrust bearing
14
and adjusting screw
15
′ threaded into center bore
8
. Axial gaps of thrust bearing
14
and thrust bearing
17
, which are described in detail later, are adjusted by controlling the degree to which adjusting screw
15
′ is threaded into center bore
8
, which thereby, adjusts the axial loads applied to thrust bearings
14
and
17
. Lip seal
34
is disposed at a front side of radial bearing
12
.
Rotor
16
is disposed in crank chamber
10
and fixed to drive shaft
11
. Rotor
16
is supported in the axial direction of drive shaft
11
by front end plate
3
via thrust bearing
17
. Arm portion
16
a
is formed by the rear end portion of rotor
16
. Slot
16
b
is defined in arm portion
16
a
. Spherical bush
18
is slidably fitted onto drive shaft
11
at a rear position of rotor
16
, in the axial direction of drive shaft
11
. Coil spring
19
is interposed between rotor
16
and spherical bush
18
. Disc-type inclined plate
20
is provided slidably and rotatably on spherical bush
18
.
Arm portion
20
a
is provided on one side of inclined plate
20
. Arm portion
20
a
extends toward selvage portion
16
a
of rotor
16
. Arm portion
20
a
has hole
20
b
defined at a position corresponding to slot
16
b
. Pin
21
is inserted into slot
16
b
and hole
20
b
to connect rotor
16
and inclined plate
20
while allowing the variable inclination of inclined plate
20
.
A pair of semi-spherical sliding shoes
22
are provided slidably on both surfaces of a radial outer portion of inclined plate
20
. A plurality of pairs of semi-spherical sliding shoes
22
are disposed radially about inclined plate
20
at even intervals. Each pair of semi-spherical sliding shoes
22
are held slidably in each piston rod
23
. Each piston rod
23
extends into a corresponding cylinder bore
7
in the rear direction, and forms a piston
24
slidably inserted into the corresponding cylinder bore
7
.
Suction port
25
and discharge port
26
are provided on valve plate
5
in correspondence with each cylinder bore
7
. A suction valve (not shown) and a discharge valve (not shown) are provided for controlling the flow of fluid through suction port
25
and discharge port
26
, respectively. Suction chamber
27
, communicating with suction port
25
, and discharge chamber
28
, communicating with discharge port
26
, are formed in cylinder head
4
. Suction chamber
27
communicates with inlet port
29
. Discharge chamber
28
communicates with outlet port
30
.
Communication path
9
, formed in cylinder block
6
, communicates with crank chamber
10
and suction chamber
27
. Bellows
31
is disposed in communication path
9
. Electromagnetic clutch
32
is provided at a front position of front end plate
3
.
In variable displacement inclined plate compressor
1
′, an external driving force is transmitted from an external drive source (not shown), via electromagnetic clutch
32
, to rotate drive shaft
11
. Rotor
16
rotates synchronously with the rotation of drive shaft
11
. Inclined plate
20
rotates synchronously with the rotation of rotor
16
. A pair of sliding shoes
22
slide on the surfaces of the radial outer portion of rotated inclined plate
20
, while moving reciprocally in the front/rear direction. Piston rod
23
, which holds sliding shoes
22
, and piston
24
, which is formed on the rear end portion of piston rod
23
, also move reciprocally in the front/rear direction in cylinder bore
7
. By the reciprocal movement of each piston
23
, fluid introduced into suction chamber
27
from inlet port
29
is drawn into cylinder bore
7
through suction port
25
. This fluid then is compressed in cylinder bore
7
and discharged into discharge chamber
28
through discharge port
26
, and then is discharged to an external fluid circuit (not shown) through outlet port
30
.
In variable displacement inclined plate compressor
1
′, when the thermal load of the external fluid circuit increases, the pressures in suction chamber
27
and communication path
9
increase, bellows
31
shrinks, and crank chamber
10
communicates with communication path
9
. Blowby gas, that has leaked from cylinder bore
7
into crank chamber
10
through the sliding portion between piston
24
and cylinder bore
7
, is released into suction chamber
27
through communication path
9
. As a result, the pressure in crank chamber
10
becomes nearly equal to the pressure in suction chamber
27
.
Referring to
FIG. 2
, in the compression process, moment Ml, which causes inclined plate
20
to rotate in the clockwise direction around pin
21
, is generated by the compression reactive force applied to piston
24
. Oppositely, moment M
2
, which causes inclined plate
20
to rotate in the counterclockwise direction around pin
21
, is generated by the expanding force of coil spring
19
. Therefore, when the thermal load of the external fluid circuit and the pressure in suction chamber
27
increase, the compression reactive force increases to a condition of M
1
>M
2
. Consequently, inclined plate
20
rotates clockwise, the stroke of piston
24
increases, and the displacement of variable displacement inclined plate compressor
1
′ increases.
When the thermal load of the external fluid circuit decreases, the pressures in suction chamber
27
and communication path
9
decrease, bellows
31
expands, and the communication between crank chamber
10
and communication path
9
is interrupted. The pressure in crank chamber
10
becomes higher than the pressure in suction chamber
27
due to blowby gas introduced into crank chamber
10
. Consequently, during the compression process, moment M
3
, which causes inclined plate
20
to rotate in the counter-clockwise direction around pin
21
, is generated by the pressure of blowby gas in crank chamber
10
. When the thermal load of the external fluid circuit and the pressure in suction chamber
27
decrease, the compression reactive force decreases, such that M
1
<M
2
+M
3
. Consequently, inclined plate
20
rotates counter-clockwise, the stroke of piston
24
decreases, and the displacement of variable displacement inclined plate compressor
1
′ decreases.
In known variable displacement inclined plate compressor
1
′, when compressor
1
′ is operated at a low thermal load condition, (a) a resultant axial force, due to the pressure of blowby gas in crank chamber
10
, is applied to drive shaft
11
via piston
2
Koczo Michael
Sanden Corporation
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